Max Planck Institute for Polymer Research , Ackermannweg 10 , D-55128 Mainz , Germany.
Department of Organic and Polymer Chemistry, College of Chemistry and Chemical Engineering , Central South University , Changsha , Hunan 410083 , P. R. China.
J Am Chem Soc. 2018 Jun 27;140(25):7803-7809. doi: 10.1021/jacs.8b02209. Epub 2018 Jun 15.
Among organic electronic materials, graphene nanoribbons (GNRs) offer extraordinary versatility as next-generation semiconducting materials for nanoelectronics and optoelectronics due to their tunable properties, including charge-carrier mobility, optical absorption, and electronic bandgap, which are uniquely defined by their chemical structures. Although planar GNRs have been predominantly considered until now, nonplanarity can be an additional parameter to modulate their properties without changing the aromatic core. Herein, we report theoretical and experimental studies on two GNR structures with "cove"-type edges, having an identical aromatic core but with alkyl side chains at different peripheral positions. The theoretical results indicate that installment of alkyl chains at the innermost positions of the "cove"-type edges can "bend" the peripheral rings of the GNR through steric repulsion between aromatic protons and the introduced alkyl chains. This structural distortion is theoretically predicted to reduce the bandgap by up to 0.27 eV, which is corroborated by experimental comparison of thus synthesized planar and nonplanar GNRs through UV-vis-near-infrared absorption and photoluminescence excitation spectroscopy. Our results extend the possibility of engineering GNR properties, adding subtle structural distortion as a distinct and potentially highly versatile parameter.
在有机电子材料中，石墨烯纳米带（GNRs）因其可调谐的性质，包括电荷载流子迁移率、光吸收和电子带隙，而成为下一代用于纳米电子学和光电子学的半导体材料，具有非凡的多功能性，这些性质是由其化学结构独特定义的。尽管迄今为止主要考虑的是平面 GNRs，但非平面性可以是另外一个参数，可以在不改变芳构核心的情况下调节其性质。在此，我们报告了具有“凹口”型边缘的两种 GNR 结构的理论和实验研究，它们具有相同的芳构核心，但在不同的外围位置具有烷基侧链。理论结果表明，在“凹口”型边缘的最内位置安装烷基链可以通过芳构质子和引入的烷基链之间的空间排斥作用“弯曲”GNR 的外围环。这种结构变形理论上预测可以将带隙降低高达 0.27eV，这通过通过紫外-可见-近红外吸收和光致发光激发光谱对合成的平面和非平面 GNR 进行实验比较得到了证实。我们的结果扩展了 GNR 性质工程的可能性，增加了微妙的结构变形作为一个独特且潜在高度通用的参数。
